The present invention relates to fluid dispersal devices and the like and, more particularly, to such a device of simple and inexpensive construction which requires relatively small fluid pressures to establish various meaningful spray patterns.
Until recently, in order to achieve spray patterns of different desired configurations, one merely shaped an orifice accordingly. Thus, a jet flow could be achieved from a simple small round aperture; a sheet flow could be achieved from a lineal aperture; swirl nozzles could be used to effect conical spray patterns; etc. This nozzle-shaping approach is simple and inexpensive but the resulting nozzles generally require relatively high applied fluid pressures in order to produce useful spray patterns.
A considerable advance in fluid dispersal devices is described in U.S. Pat. No. 4,052,002 to Stouffer et al. Stouffer et al describe a fluidic oscillator arranged to issue a transversely oscillating fluid jet which, because of the oscillation, distributes itself in a fan-shaped sheet pattern residing in a plane. The interaction of a liquid jet with ambient air results in the jet breaking up into droplets of uniform size and distribution along the fan width. The oscillations begin at relatively low applied fluid pressures (on the order of 0.1 psi) so that fluid dispersal may be efficiently effected at low pressures. This fluidic oscillator approach to fluid dispersal is quite advantageous but is limited in that the issued spray pattern is planar and therefore impinges linearly on a target surface. In many applications it is desirable to provide spray patterns of two-dimensional cross-section which cover a two-dimensional area target.
Other approaches to fluidic nozzles, similarly limited to linear target impingement, are found in U.S. Pat. Nos. 3,423,026 (Carpenter); 3,638,866 (Walker); and 3,911,858 (Goodwin). However, these approaches have the additional disadvantage of requiring higher threshold pressures than the Stouffer et al oscillator before a desirable spray pattern can be achieved.
Area or two-dimensional target impingement can be achieved with a fluidic oscillator as described in U.S. Pat. No. 3,820,716 (Bauer). However, in that approach the oscillator itself must be formed in a three-dimensional annular configuration which is more complex and expensive to manufacture than the more familiar planar configuration of fluidic oscillators. Further, the pressure threshold required to produce oscillation is considerably higher in the Bauer oscillator than in the Stouffer et al oscillator.
The present invention is not truly a fluidic oscillator in that it involves use of the phenomenon known as the Karman vortex street. This phenomenon, well known in the field of fluid dynamics (reference: Handbook of Fluid Dynamics, Victor L. Streeter, Editor-in-Chief, McGraw-Hill Book Company, 1961, page 9-6) relates to a pattern of alternating vortices which are shed on opposite sides of an obstacle disposed in the path of a fluid stream. In the prior art, primary concern over vortex streets has been in the area of fluid-dynamic drag wherein the obstacle (e.g. a wing or fin) is to be moved through a fluid medium with minimal disturbance. The present invention makes use of this vortex street phenomenon in an entirely new context to disperse fluids with a greater variety of dispersal patterns than provided by fluidic oscillators yet with all the advantages inherent in fluidic technology.
It is therefore a primary object of the present invention to provide an improved method and an improved device for dispersing fluids.
It is another object of the present invention to provide a fluid dispersal device which, like fluidic oscillators, is simple and inexpensive to manufacture, issues oscillating fluid streams and has no moving parts but, unlike conventional fluidic oscillators, is capable of dispersing fluid over an area target as well as a linear target.
It is another object of the present invention to utilize the vortex street phenomenon to effect fluid dispersal.